1. Field of the Invention
The present invention relates to a handling apparatus for transferring, one by one, sheet-like objects such as semiconductor wafers or Liquid Crystal Displays (LCDs) and, more particularly, to a handling apparatus having a link mechanism which can be folded into a compact size.
2. Description of the Related Art
In the process of manufacturing semiconductor devices such as ICs and LSIs, semiconductor wafers are handled in a clean, dust-free room so as to prevent contamination of the micropatterned surfaces of semiconductor wafers by the attachment of particles such as dust thereto. A means for transferring semiconductor wafers in a clean room is a transporting mechanism of a belt conveyor or mechanical handle type. In particular, in processes such as etching and ion implantation which require a clean, dust-free environment a special handling apparatus is used in order to load or unload semiconductor wafers into/from a vacuum chamber, one by one. A sheet handling apparatus must satisfy requirements (1) and (2) so as to shorten the vacuum processing time and maintain a clean, dust-free environment:
(1) A space required for the handling apparatus during nonuse is small, and a transporting distance of the apparatus is long; and
(2) The amount of dust generated during use of the apparatus is small.
In recent years, various types of handling apparatuses which satisfy the above requirements have been developed. A compact handling apparatus which generates a very small amount of dust is commercially available.
Semiconductor wafer handling apparatuses are disclosed in Japanese Utility Model Disclosure (Kokai) No. 60-61191 and Japanese Patent Disclosure Nos. 60-183736 and 61-160949. These handling apparatuses utilize "pantagraphs" as the arm of the transporting mechanisms.
More compact handling apparatuses are disclosed in Japanese Patent Disclosure Nos. 61-90903, 61-87351, and 61-90887.
In order to reduce the space required for storing conventional handling apparatuses during nonuse, the length of the arm of the pantagraph and the number of joints therein have been reduced, thereby limiting the area for transporting the objects to be processed. However, in the case wherein the transportable area is increased by lengthening the arm of the pantagraph and increasing the number of joints therein so as to increase the area for transporting the objects to be processed, the size of the apparatus during nonuse is undesirably increased.
A strong demand has arisen for processing semiconductor wafers, one by one, along with development of 4 and 16-mega-bit devices in accordance with an advance of VLSI techniques. In order to increase the throughput of such a sheet handling apparatus, a load lock mechanism is employed in the conventional handling apparatus. In order that such a load lock mechanism be provided, a dust-free transporting mechanism is required. It is very important to transport a larger wafer within a limited area due to dust-free.
A chamber for containing the handling apparatus and the vacuum chamber for processing the semiconductor wafer are partitioned by a gate valve. When the gate valve is open, the chamber (container) for containing the handling apparatus communicates with the vacuum chamber (container). Therefore, it takes a long period of time to remove the air from the vacuum chamber.
Furthermore, in a conventional handling apparatus, a substantial amount of dust is generated as compared with that of a drive mechanism in the handling apparatus. Dust enters and contaminates the vacuum chamber via the handling apparatus container.
In particular, in a clean room for handling VLSIs having a high integration density, the degree of cleanliness required is class 10 or higher. Therefore, since the conventional handling apparatuses do not meet this requirement, they are not suitable for handling VLSI semiconductor wafers.